根圏土壌のプロテアーゼ活性の作物間比較 : 有機態窒素の吸収および吸収機構の作物間比較(第3報)

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Previously, we showed that upland rice (Oryza sativa L.) had a higher response to organic nitrotgen applied as rice bran than maize (Zea mays L.). We proposed three hypotheses for the results. Firstly, rice has a greater ability to compete with microorganisms for inorganic nitrogen. Secondly, rice is superior in the uptake of ammonium, amino acids and peptides. Thirdly, the mineralization in rice root zone occurs more actively as compared to other crops. We investigated the protease activity in the soil to clarify how much the third hypothesis contributed to the nitrogen uptake of rice, We cultivated rice, maize and soybean (Glycine max Merr.) in small pots (5 × 5 × 5 cm) with Andosol in a glasshouse at the National Institute of Agro-Environment Sciences, Tsukuba, Japan, in 1995. We took the soils in rhizosphere and non-rhizosphere separately 26 and 34 d after sowing, and then measured the protease activity of these soils using casein and Z-phe-leu as the substrates. The soil protease activity of maize was higher than that of rice, and soybean was found to be the medium of these crops. These results show that the rhizosphere effect related to nitrogen mineralization such as protease activity does not specifically occur in rice cultivation soil. The other hypotheses are to be investigated to enable comprehension of the strong ability of nitrogen uptake by rice.
社団法人日本土壌肥料学会の論文
1997-06-05